Bath for electrolytical separation of copper with high-grade mechanical properties



United States Patent 3,360,447 BATH FOR ELECTROLYTICAL SEPARATION OF COPPER WITH HIGH-GRADE MECHANICAL PROPERTIES Lubomir Svatek, 102 Prazska, Ujezd nad Lesy, Czechoslovakia, and Jaromir Vitek, 4 Piseclra, Prague 3, Czechoslovakia No Drawing. Filed Mar. 1, 1965, Ser. No. 436,332 Claims priority, application Czechoslovakia, Mar. 11, 1964, 1,391/64 7 Claims. (Cl. 204-52) The invention relates generally to the separation of metallic copper having advantageous mechanical properties whereby the copper is isolated from an acid copperplating bath containing an addition agent comprising a mixture of selected organic and inorganic materials.

Metallic copper of a high hardness is required in such varied uses as the production of galvanoplastic molds for pressure die casting and mold pressing of plastic materials, in the welding technology for producing electrodes for spot and seam welding, in electroerosive machining, and the like.

However, it has been found that whereas copper is otherwise very advantageous in the production of galvanoplastic molds, ordinary metallic copper does not possess the necessary good mechanical properties. Copper obtained by known electrolytical methods is relatively rather soft. Its hardness does not exceed about 45 to 50 H degrees in the Vickers hardness scale. Because of this deficiency such molds possess only a short life under actual production conditions.

Welding techniques and technology also require hard electrodes with a high electrical conductivity. The use of pure electrolytic copper with a high electrical conducductivity is not convenient because of its low mechanical properties. Therefore, copper alloys containing tungsten, chromium, beryllium and alloying materials are used which raises the hardness up to about 200 H but as a consequence, the electrical conductivity is reduced. In addition, at points where the electrodes come into contact with the welded material, the increased resistance leads to a rather high local heating of the electrodes and this effect further reduces electrode life. The life of commutators, collectors, and other parts of electrical rotatingfield machines is limited by the low mechanical properties of the copper metal.

Electrolytic copper of high hardness is also required in electric spark machining because the electrodes employed including those of the most complicated shapes can be produced by galvanoplastic methods. Again electrolytically separated copper does not give the required mechanical properties for this machining process, and is particularly deficient as respects hardness.

It is therefore a general object of this invention to eliminate the aforesaid disadvantages of the prior art in the copper-plating process.

Another more specific object of the invention is to obtain copper with very good mechanical properties, particularly with a high hardness from an electrolytic process.

Still another object of the invention is to obtain copper for electroplating processes which has the necessary hardness together with the necessary electrical conductivity.

The invention provides an addition agent for an acid copper-plating bath with a pH-value 0.4 to 1.5 causing separation of copper with high mechanical properties, particularly high hardness and resistance to abrasive wear.

The novel addition agent is a combination of ingredients in critical amounts. The components are 40 to 60 percent by weight of absolute ethyl alcohol, 30 to 40 percent by weight of glacial acetic acid, 0.2 to 0.4 percent ICC by weight of gelatin, 0.5 to 0.7 percent by weight of casein, and from 10 to 20 percent by weight of concentrated sulfuric acid.

The mixture of components which comprises the addition agent is added to an acid copper-plating bath at the ratio of 1,00021 to 25:1 relative to the volume of the bath. The addition of the additive agent is done in the customary way and gives no unusual problems.

It is a further advantage of this process that the electrolytic process for plating from the electroplating bath is carried out in the usual conventional way under Wellknown conditions to give the improved copper metal having increased hardness.

As the result of the addition of the additive agent, in accordance with the process of the invention, the copper which is separated out in the bath has a hardness of up to 250 H and higher and also possesses a high resistance to abrasive wear. Its structure is believed to be essentially microcrystalline, the surface is smooth, and its electrical conductivity is about equivalent to that of standard electrolytic copper. It can be easily machined by standard methods.

All these improved properties eliminate technical problems in various technological branches. The plating bath prepared in'accordance with the process of the invention may be conveniently used in the production of galvanoplastic molds. Such molds produced by the improved process preserve the general advantages of the galvanoplastic production and in addition, exhibit much longer life. The improved electroplating bath may also be used in the production of tools for electroerosive machining. Tools produced in this manner have a very long life and also show high electrical conductivity. The use of the bath also permits the production of hard copper coatings which are resistant to abrasive wear.

Electrolytic copper with high hardness properties as obtained from the bath comprising the novel addition agent can be readily used for producing welding electrodes for spot and seam welding. Electrodes produced from this hard copper possess properties which are better than the properties of known copper alloy electrodes of highest quality and their electrical conductivity is also much higher.

The improved properties result in economy in electrical energy as well as in increased electrode life. There are many other possibilities of successfully applying the invention and obtaining useful results therefrom; for example, in parts of electrical machines which are subjected to mechanical stress, particularly friction. Typical uses include commutators, collectors, components of switches, and the like. The life of a commutator using standard copper was tested to be 2,000 hours. The same commutator with active surfaces provided with a layer of hard copper obtained in accordance with the invention had a life of at least 20,000 hours when tested under the same conditions.

Example 1 To each liter of a standard typical acid copper-plating bat-h comprising 220 g./l. of cupric sulphate (CuSO and having a pH-value of 0.4 to 1.5, are added 20 ml. of the premixed addition agent made up to the following composition:

If a current density of 3 amperes per decimeter squared (3 a./dm. is used, the hardness of the separated copper is 2001-4 H If the amount of addition agent described above is increased to the ratio 25 :1, the hardness of the separated copper rises proportionally to a value H 250 and higher.

Example 2 To each liter of an acid copper-plating bath are added 40 ml. of the addition agent of the following composition:

Absolute ethyl alcohol ml 1300 Gelatin g 6 Casein g 14 Concentrated sulfuric acid ml 250 Glacial acetic acid ml 600 The hardness of the copper obtained from this electrolytic bath is 265 H If the content of the addition agent in the bath is reduced, the hardness of the separated copper is also reduced.

Example 3 To each liter of an acid copper electrolytic bath are added 5 ml. of an addition agent of the following composition:

Absolute ethyl alcohol ml 1100 Gelatin g 8 Casein g 12 Concentrated sulfuric acid ml 300 Glacial acetic acid ml 500 The hardness of the metallic copper therefrom is 140: H

As can be seen from the above examples of carrying out the invention, the obtained hardness of the separated copper is very closely related to the amount of the addition agent in the bath. This permits, if desired, the construction of a graph for reading, for example, the appropriate amount of the addition agent to be used in accordance with the invention to obtain a desired product result.

While the foregoing examples described a number of embodiments of the invention, it is to be understood that it is in no way intended to limit the invention specifically thereto. Unless otherwise specified, all parts are given in percent by weight.

What is claimed is:

1. An improved aqueous acid copper-plating bath having present therein a soluble copper salt and at least 1 part by volume per 1000 parts of acid bath of an additive material consisting essentially of 40 to 60 weight percent of absolute ethyl alcohol, 30 to 40 weight percent of glacial acetic acid, 0.2 to 0.4 weight percent of gelatin, 0.5 to 0.7 weight percent of casein, and 10 to 20 weight percent of concentrated sulfuric acid.

2. The bath of claim 1, having a pH of 0.4 to 1.5 and wherein said copper salt is cupric sulfate.

3. The bath of claim 1, having a pH of 0.4 to 1.5 and wherein said additive material is present in the ratio of 1,000:l to :1 parts by volume of bath.

4. An improved aqueous acid copper-plating bath as described in claim 1 which contains per liter of acid copper plating bath, about 20 ml. of said additive material consisting essentially of 1000 ml. of absolute ethyl alcohol, 5 g. of gelatin, 10 g. casein, 200 to 300 m1. of concentrated sulfuric acid and 500 ml. of glacial acetic acid.

5. An improved aqueous acid copper plating bath as described in claim 1 which contains per liter of acid copper plating bath, about 40 ml. of said additive material consisting essentially Of 1300 ml. of absolute ethyl alcohol, 6 g. of gelatin, 14 g. of casein, 250 ml. of concentrated sulfuric acid and 600 ml. of glacial acetic acid.

6. An improved aqueous acid copper plating bath as described in claim 1 which contains per liter of acid copper plating bath, about 5 ml. of said additive material consisting essentially of absolute ethyl alcohol, 8 g. of gelatin, 12 g. of casein, 300 ml. of concentrated sulfuric acid, and 500 ml. of glacial acetic acid.

7. An additive for an acid electroplating bath consisting essentially of 40 to weight percent of absolute ethyl alcohol, 30 to 40 weight percent of glacial acetic acid, 0.2 to 0.4 weight percent of gelatin, 0.5 to 0.7 weight percent of casein and 10 to 20 weight percent of concentrated sulfuric acid.

References Cited UNITED STATES PATENTS 2,271,209 l/ 1942 Schlotter 20452 X 2,680,711 6/1954 Norwitz 204-52 2,733,198 1/1956 Nobel et al 20452 2,888,390 5/1959 Lapee 20452 X HOWARD S. WILLIAMS, Primary Examiner.

G. KAPLAN, Assistant Examiner. 

1. AN IMPROVED AQUEOUS ACID COPPER-PLATING BATH HAVING PRESENT THEREIN A SOLUBLE COPPER SALT AND AT LEAST 1 PART BY VOLUME PER 1000 PARTS OF ACID BATH OF AN ADDITIVE MATERIAL CONSISTING ESSENTAILLY OF 40 TO 60 WEIGHT PERCENT OF ABSOLUTE ETHYL ALCOHOL, 30 TO 40 WEIGHT PERCENT OF GLACIAL ACETIC ACID, 0.2 TO 0.4 WEIGHT PERCENT OF GELATIN, 0.5 TO 0.7 WEIGHT OF CASEIN, AND 10 TO 20 WEIGHT PERCENT OF CONCENTRATED SULFURIC ACID. 